1. Field
The present disclosure relates generally to impact testing and in particular to a method and apparatus for in-situ measurement of impacts caused by hail stones.
2. Background
Hail is a form of precipitation and may include balls or irregular lumps of ice. Hail is also referred to as hail stones. Hail stones may form in clouds when super-cooled water droplets freeze on contact with condensation nuclei, such as dust. Up drafts in the storm may blow or push hail stones to the upper part of the cloud. The hail stones may then fall down when the up draft dissipates. This cycle may occur a number of times with the hail stone, gaining a layer of ice each time the hail stone ascends.
Hail stones may cause damage to a number of different man made objects such as houses, office buildings, cars, trucks, aircraft, and other man made objects. With respect to aircraft, the type of materials, thickness of materials, and other parameters with respect to materials for an exterior portion of the aircraft may include consideration as to how these materials may react when hail stones impact different parts on the aircraft. These parts include, for example, without limitation, a windshield, a wing panel, an aileron, a jet engine inlet, a fuselage, and other suitable exterior components of an aircraft.
In designing these and other components for an aircraft, projections may be made to provide some minimum gauge or thickness to take in to account hail stone impacts on those components. Currently, in identifying minimum thicknesses for components, simulations are used to predict how these components will be affected by impacts caused by hail stones.
One currently used method employs rubber balls to simulate the impact of hail stones. Other currently used methods may simulate hail stone impacts by using a composite ice ball, such as cotton with frozen water. Another approach may use lead or steel balls to simulate hail. These different types of simulations provide some ability to predict the effects of strikes or impacts caused by hail stones. The use of simulated hail stones, such as rubber balls and man made hail stones, provide useful information for designing aircraft parts. These currently used methods are useful, but are only rough simulations of hail stone impacts.
As a result, different designs for aircraft parts may over compensate for the effects of hail stone impacts. Therefore, it would be advantageous to have a method and apparatus that overcomes the problems described above.